This invention relates to a piezoelectric element device circuit with a improved power efficiency.
The use of piezoelectric elements has been proposed to drive wires in a matrix printer or an ink particle generating system in an inlet printer. Such a piezoelectric element is driven by an exemplary drive circuit as shown in FIG. 7. The piezoelectric element 2 shown is to be connected to a direct-current power source 1 via a transistor 3 so that it receives voltage from the source 1 when the transistor 3 is turned on by a print start signal S1. The element 2 expands or contracts with the voltage applied thereto. This displacement is then magnified by a transfer unit to drive a wire as in a printing mechanism. Because the piezoelectric element 2 serves as a capacitor, the charged element 2 is kept expanded or contracted if the transistor 3 is turned off, so that the print mechanism is not allowed to restore its original position. This problem is solved by providing a transistor 4 connected in parallel with the piezoelectric element 2 via a resistor 10, which is kept on for a certain length of time in response to a print end signal S2 after print is completed. This allows the piezoelectric element 2 to discharge to turn the voltage to zero whereby the print mechanism is allowed to restore its original position.
In this arrangement, the charge stored within the piezoelectric element 2 is lost as resistance loss so that the element 2 must be re supplied with power from the direct-current power source 1 to be driven again. This entails a significant power loss and therefore a reduced power efficiency during driving the printing mechanism.